Plant for continuous vacuum casting of metals or other materials

ABSTRACT

The invention relates to a method for continuous vacuum casting of metals or other materials and a plant for effecting said method more particularly for the obtention of shapes and tubes. The method applicable to plants comprising a spray means in the open air and a dynamic lock for emergence into air,comprised of chambers which are maintained under decreasing pressures by pumping devices of known types and are separated from each other by diaphragms, consists, on the one hand, in holding the static pressure of the metal on the shape or tube being formed at a constant value, for a given size with respect to the liquid meniscus size, so as to render the permissible difference between the cross-section of said shape or tube, when reaching the dynamic lock, and the cross-section of said diaphragms low enough for the rate of air admission to remain in all cases lower than the pumping rates of said pumping devices, and, on the other hand, in so selecting the cooling zone length, as a function of the suitably set rate of withdrawal of the moulded shape, that said shape will enter the spray means, when leaving the lock, at a constant, controlled temperature. The invention is especially applicable to the obtention of uranium shapes or tubes.

United States Patent 1191 Chaulet et a1.

1 11 3,724,529 1451 Apr. 3,1973

1541 PLANT FOR CONTINUOUS VACUUM CASTING OF METALS OR OTHER Guichard,Voiron; Pierre Lucien Menissier, Grenoble; Jean-Claude Georges Soret,St. Egreve, all of France [73] Assignee: Societe Anonyme SocieteIndustrielle de Combustible Nucleaire, l-laute Savoie, France [22]Filed: Oct. 13, 1969 [21] Appl. No.: 865,719

[30] Foreign Application Priority Data 2,935.395 5/1960 Smith ..164/64 x3,148,420 9/1964 Hess 164/260 3,395,751 8/1968 Hess ..164/260 3,414,04712/1968 Saunders.... ....164/283 3,461,950 8/1969 Michelson ....164 2603,528,483 9/1970 Mallener ..164/260 Primary ExaminerJ. SpencerOverholser Assistant Examiner-John S. Brown Attorney-Baldwin, Wight andBrown [57] ABSTRACT The invention relates to a method for continuousvacuum casting of metals or other materials and a plant for effectingsaid method more particularly for the obtention of shapes and tubes.

The method applicable to plants comprising a spray means in the open airand a dynamic lock for emergence into air,comprised of chambers whichare maintained under decreasing pressures by pumping devices of knowntypes and are separated from each other by diaphragms, consists, on theone hand, in holding the static pressure of the metal on the shape ortube being formed at a constant value, for a given size with respect tothe liquid meniscus size, so as to render the permissible differencebetween the cross-section of said shape or tube, when reaching thedynamic lock, and the cross-section of said diaphragms low enough forthe rate of air admission to remain in all cases lower than the urn inrates of said m in devices, and, on the 08181 arid, in so selecgl ng thcooling The invention is especially applicable to the obtention ofuranium shapes or tubes.

7 Claims, 8 Drawing Figures PATENTED I975 D 3.724 529 sum 1 0F 4 Fig. 2

PATENTEU B I973 SHEET 4 BF 4 Wm: Pwu L m PLANT FOR CONTINUOUS VACUUMCASTING OF METALS OR OTHER MATERIALS The present invention relates to aplant for performing a method for continuous vacuum casting of metals,metal alloys or other materials which require good degassing and/or areliable to readily react at high temperature under normal atmosphericconditions, said method being especially suitable for the manufacture ofuranium shapes and tubes.

The increasing trend to use very pure metals or alloying elements,coupled with the need to prevent oxidation of said metals during thevarious handling steps in a shapeor tube-making process, has led toconstant improvements in the methods used in such processes and in theapparatuses for their operation.

Devices are already known whereby tubes, shapes and bars consisting of asheath surrounding a core of a different material can be continuouslycast and shaped in the open air, but such procedures lack advantagesgained by operating under vacuum or under reduced neutral gas pressurein accordance with the present invention.

Devices are also known whereby materials can be cast under vacuum, butno means providing the advantages of the present invention has beenheretofore provided for continuous withdrawal of these materials fromunder vacuum, particularly if use is to be made of relatively highvacuum.

Finally, previously known apparatuses for the socalled continuous"vacuum casting include no device having the advantages of the presentinvention for continuous withdrawal of the hot metal from under vacuuminto air.

Moreover, no means have previously been provided to ensure thecontrolled cooling and, if required, the hardening of the metal in asingle step according to the present invention.

The present invention is directed to improve the aforesaid methods anddevices so as to provide a method and plant whereby the steps of vacuumdegassing, continuous vacuum casting and controlled cooling of metals,metal alloys or other materials, especially those liable to readilyreact at high temperature under normal atmosphere, can be effectedsimultaneously.

The method according to the invention is especially applicable to plantscomprising a ladle containing molten metal held at constant temperature,or any other isothermal source of molten metal; a cooled ingotmould,also adapted to serve sometimes as a ladle; a vacuum cooling device and,between said vacuum cooling device and a spray means in the open air, adynamic lock for emergence into air, comprised of chambers which aremaintained under decreasing pressures by pumping devices of known typesand are separated from each other by diaphragms.

The aforesaid method consists, on the one hand, in holding the staticpressure of the metal on the shape or tube being formed at a constantvalue, for a given size with respect to the liquid meniscus size, so asto render the permissible difference between the cross-section of saidshape or tube, when reaching the dynamic lock, and the cross-section ofsaid diaphragms low enough for the rate of air admission to remain inall cases lower than the pumping rates of said pumping devices, and,

on the other hand, in so selecting the cooling zone length, as afunction of the suitably set rate of withdrawal of the moulded shape,that said shape will enter the spray means, when leaving the lock, at aconstant, controlled temperature.

The plant for operating to perform said method comprises in combinationa vacuum chamber, a ladle located within said vacuum chamber; aflow-rate control system associated with the ladle, such as anelectromagnetic pump or a plunger in the lower part of said ladle; adistributor provided with a nozzle and fed with the liquid metalreleased by the plunger; a replaceable ingot-mould with a water-coolingsystem; a level-detector arranged within the mould and adapted tocontrol a servo-mechanism acting to adjust the flow-rate controllingmeans, eg the plunger position; a cooling jacket; a dynamic lockcomprising several suction chambers, each connected to a pump of a typedepending on the pressure in the respective chamber, said chambers beingseparated from each other by diaphragms and the last of them beingfollowed by a pneumatic seal consisting of a neutral gas blast whichacts moreover as a cooling device; a cooling spray device locatedoutside the vacuum chamber at the outlet of said dynamic lock;withdrawal and guiding rollers rotating at a rate which can be adjustedby a servomechanism under the control of a temperature detector arrangedat the outlet of the vacuum cooling chamber and, finally, aningot-cutting device of any known type.

For the manufacture of tubes with a core, the plant comprises moreover adynamic lock for inserting the core into the vacuum chamber; a guidingunit adapted to feed said core in true axial alignment with the mouldand formed of roller sets arranged on each side of the dynamic lock and,if required, a core-heating device, either in front of the dynamic lockor under vacuum between said lock and the mould.

ln case where the plant includes a vacuum core-heating device, then thedynamic lock may be simplified and include from outside to inside thevacuum chamber a sliding, preferably double-walled seal surrounding thecore and made of elastomer, a suction chamber connected to a highdischarge pump and a threaded dynamic seal.

Finally, in another embodiment devised to solve the problems raised bythe tendency of the solidifying metal to stick to the inner wall of themoulds and by the control of the liquid material level, the apparatuscomprises means for vibrating the mould according to a definite mode andfor controlling with high precision the level reached in the mould bysaid liquid materials, and said means will be described in details inthe following.

As a matter of fact, such sticking is known to impair the quality of thecast metal and to limit to some extent the speed at which the bars canreach the mould outlet, but the sticking effects can be reduced byvibrating the ingot-moulds. On the other hand, the rate at which theliquid materials are fed to the mould can be deemed well adjusted if thelevel of said liquid materials in the mould remains constant.

The invention will now be described in more details, with reference tothe acoompanying drawings, wherein:

FIG. 1 is a diagrammatical lay-out of a plant for the continuous vacuumcasting of a bar.

FIG. 2 is a detailed enlarged view of the dynamic lock.

FIG. 3 shows a dynamic seal.

FIG. 4 shows the pneumatic seal and the associated spray means.

FIG. 5 is a diagrammatic lay-out of a plant for the continuous vacuumcasting of tubes including a core.

FIG. 6 is a diagrammatic view showing the setting of an external ladlefor make-up metal.

FIG. 7 shows the mounting of an ingot-mould which is caused to vibrateand of a system for controlling the level of the liquid materials insaid ingot-mould, according to the invention, and

FIG. 8 is a reduced scale, schematic perspective view of a cam mechanismfor vibrating an ingot mould vertically.

As shown in FIG. 1, the plant comprises a vacuum chamber 1, havinglocated therein a ladle 2 acting as a reservoir for the liquid materialused, in the example illustrated, for the manufacture of bars.

The ladle 2 is surrounded by an induction heating electric coil 3.

In the lower portion of ladle 2 is located a plunger or stopper 4 whichcontrols the exit of liquid material from said ladle and has its openingmovement controlled in very precise manner from a mechanical device 5under the control of a servo-mechanism 6.

Under ladle 2 is a funnel-shaped distributor 7 which receives the liquidmaterial descending past the plunger 4 and pours the same into a nozzle8 ensuring uniform flow of the liquid material from the distributor 7into an ingot-mould 9 adapted to shape the liquid flowing therethrough.The ingot-mould 9 is replaceable and of known type; its internal portionis cylindrical and has a cross-section substantially equal to that ofthe bars to be produced, taking into account the shrinkage of thesolidifying and cooling metal. The internal portion of the ingot-mouldmay also be slightly tapering off downwards, at an angle of l2, so as topartly compensate shrinkage and thus prevent too rapid impairment of thethermal contact between the ingot and the mould.

The ingot-mould 9 is provided within its wall with a hydraulic coolingcircuit supplied by ducts 10 at an adjustable flow-rate. A vibratingdevice of known type described hereinafter, is adapted to reciprocatethe ingot-mould along its axis.

Two level-sensing cells 11 and 12 are located one above the other inrecesses provided in the cylindrical portion of the mould and provide alevel detector connected to the servo-mechanism 6 which operates themechanical device 5. The level of liquid metal in the ingot-mould 9 maybe observed through an inspectionhole 13. Beneath the ingot-mould is acooling jacket 14 through which the bar passes as it emerges from theingot-mould.

Beneath the cooling jacket 14 is a dynamic vacuum lock 15 fed withnitrogen by a source 16, under a pressure controlled by aservo-mechanism l7 operated by a temperature-detector 18 at the lowerpart of the lock.

At the exit of the lock 15, the bar is driven through a spray means 19whereby it is cooled and hardened if required, then it is gripped by theroller sets 20, 20 act ing to guide it and to withdraw it from the lock.

The rollers 20, 20 are driven by a motor 21 which is operated by aservo-mechanism 22 under the control of a temperature-detector 23located at the exit of the cooling jacket 14.

A follower cutter 24 of known type can be arranged beyond rollers 20, 20to saw the ingot at a given length, normally to its axis.

When starting the continuous production of a bar, a withdrawal means 25is used to grip the bar an pull it from the ingot-mould 9.

Said withdrawal means 25 consist of a rod having exactly the samecross-sectional area as the uranium or other bar to be produced and isequipped with a simple, easy to disconnect lug device 26 of the dovetaillug type, such as found in the conventional known continuous castingplants.

As shown in FIG. 2, the dynamic lock 15 includes five suction chambers27, 28, 29, 30 and 31 and a pneumatic seal 32. The suction chambers areseparated from each other by dynamic seals 33, 34, 35, 36 and 37.

The dynamic seals 33, 34, consist of borings in inserted metalcylinders, adapted to receive the bar with a clearance of some tenths ofa millimeter, e.g. of 0.8 mm, and which may be knurled or threaded to adepth of some tenths of a millimeter.

In another embodiment, a seal may also be formed, as shown in FIG. 3, ofa flat ring 38 beating on its upper and lower faces respectivefunnel-shaped diaphragms 39, 40. Said diaphragms comprise annular plates41, 42 supported respectively on the upper and lower faces of ring 38,and, frusto-conical portions 43, 44, each of which is in fluid-tightconnection with one annular plate 41, 42 and terminates in a cylinder45, 46.

Diaphragms 39, are slit along a generatrix, so that the diameters oftheir cylindrical portions can vary by some tenths of a millimeter. Thediaphragms are secured to ring 38 in such manner that the slits are inopposite directions with respect to the axis of the dynamic seal.Theinternal diameter of cylinder 45 is substantially equal to the diameterof the bars to be produced and the inner diameter of cylinder 46 isequal to the outer diameter of cylinder 45, the whole length of thecylinder 46 engages cylinder 45 along its whole length.

Referring to FIG. 2, suction chamber 27 is connected to a low pressure,mean delivery pump (not shown). Chambers 28, 29, 30,31 are connectedthrough passages 27a, 28a, 29a, 30a and 31a to pumps (not shown) ofsuccessively increasing delivery ratings. Chamber 31 is connected to aliquid ring vacuum pump. Pumps of this type are well known, for exampleas shown in United States Pat. Nos. 1,849,929 to Hayton and 2,136,508 toStelzer. Chamber 27 is equipped with a vacuum gauge 47. Chamber 28 isconnected to a pressure-gauge 48. Pneumatic seal 32 (FIG. 4) consists oftwo moulded parts of revolution 49, 50. The upper face 51 of part 49 isflat so as to be connectable with chamber 31. The lower portion of part49 includes a frustum of revolution 52 having its axis along the axis ofthe bar being cast. Part 49 is provided along its axis with a bore of adiameter equal, but for the clearance of 0.8 mm, to the diameter of thebars to be produced.

The interior of part has the shape of a nozzle neck of which portion 53forms the converging section and portion 54 of the diverging section. Astatic seal 55 is located between the upper edge of part 50 and thelower edge of part 49. The space between parts 49 and 50 forms thepressure chamber PC which is connected by means of a pipe 56 to thesource 16 of neutral gas, preferably nitrogen, under pressure.Thefrustum 52 and portions 53, 54 of part 50 define a crown-shaped nozzlefrom which the neutral gas from pressure source 16 is released aroundand over the cooling bar. The temperature detector 18, lodged in arecess provided in the cylindrical hole of part 49, is connected toservomechanism 17.

The spray means 19 consists of a water chamber 58 the walls of which aremade of two metal bells, 59, 60 having the same axis of revolution. Eachbell is formed in its upper portion with an aperture havingsubstantially the same cross-section as the bar to be produced.Smallorifices are unifonnly distributed across bell 60. A metal pipe 61having its end welded onto bell 59 feeds water under pressure to waterchamber 58.

The continuous vacuum casting plant which has just been described bymere way of example is devised for the production of uranium bars. FIG.5 shows a modified embodiment of said plant, wherein the latter isadapted to produce uranium tubes with a graphite core.

According to this embodiment, the various units are substantiallysimilar to those of the continuous vacuum casting plant for bars, butsome of them are located differently and arranged to receive a graphitecore.

As shown in FIG. 5, the graphite core 62 has the shape of a bar and isheld in a vertical position by two sets of silicon carbide rollers 63,63'.

The graphite core 62 enters vacuum chamber 1 through a dynamic lock 64which may be identical to the afore-described dynamic lock for the exitof the moulded shape. A lock of this type must be provided whenever thecore is to be heated before entering the vacuum chamber. However, whenthe core is heated under vacuum, dynamic lock 64 is of simplifiedconstruction since it comprises from outside to inside, a double-walledcircular sliding seal 65, a suction chamber 66 with its high deliverypump and a threaded dynamic seal 67, similar to the above-describedseals 33, 34, 35.

Core 62 will then advance through means comprising a set of guidingrollers 68 located above the inlet of ingot-mould 9 and through anelectrical induction heating coil 69 before entering the ingot-mould.

Rollers 68 may to advantage be replaced by three friction padsimmediately above the connection of spout 8 with the ingot-mould.

As in the continuous vacuum casting plant for solid bars, theingot-mould 9, cooling jacket 14 and vacuum lock 15 are intended toreceive the bar to be vacuum cast and are to this end arranged invertical alignment. However, the common vertical axis of theingot-mould, cooling jacket and vacuum lock coincides with the graphitecore axis and is therefore offset with respect to the ladle 2 containinga reserve of molten metal. Spout 8 is not vertical, but oblique forfeeding the molten metal from plunger 4 to ingot-mould 9. From thelatter, the graphite core 62 with the surrounding cast ingot metal isdriven through the same units as was the bar in the continuous castingplant for bars while being kept in precise axial alignment by thesuccessive sets of silicon carbide rollers 63, 63'.

In FIG. 6, there is shown the setting of a ladle 70 containing make-upliquid metal, which has its bottom removably connected in fluid-tightmanner with vacuum chamber 1, by means known per se. Plunger 71 can beoperated from outside to pour the content of ladle 70, through the wallof vacuum chamber 1, into ladle 2, at the desired rate.

When casting a metal such as uranium, the latter is poured in the liquidstate in ladle 2, e.g. from ladle 70 which is brought on site. Ladle 2is held at a constant temperature by the induction heating coil 3. Oncethe ladle has reached the desired temperature, then liquid uranium maybe released by plunger 4.

Liquid uranium is poured in ingot-mould 9 across plunger 4 and throughspout 8. Both level-detectors 1 1 and 12 act in known manner onservo-mechanism 6 which, through mechanical device 5, will so controlthe opening movement of plunger 4 as to keep the surface of the liquiduranium in the ingot-mould between the two levels defined by saidlevel-detectors.

Upon contacting the cold wall of the ingot-mould, the metal solidifiesto form a solid skull or skin surrounding the liquid; as heat isextracted from the ingotmould, the thickness of said skull will increaseuntil the bar is formed during its descent, the bar has the samecross-section as the ingot-mould until the shrinkage caused byperipheral solidification and cooling will apply to the thickening skulla pressure exceeding the static pressure of the metal, at which time thecrosssection of the bar is then slightly smaller than that of theingot-mould. The ingot-mould is replaceable to allow changeover toanother ingot size or replacement in case of wear. It must be of suchlength that, taking into account the withdrawal rate and coolingefiiciency, the solidifying wall has acquired enough strength to retainthe metal remaining liquid in the central portion of the bar beforeleaving the ingot-mould. 0n the other hand, the ingot-mould should notbe too long, to avoid undue friction against the ingot being withdrawn.The device for vibrating the ingot-mould serves to limit the prejudicialeffects caused by said friction along the ingot surface.

At the beginning of a run, the withdrawal means 25 is introduced intovacuum chamber 1, through dynamic lock 15, its rod having the samediameter as the bar to be produced, then the lock is closed. The lug 26at the end of the withdrawal means is arranged within the cylindricalportion of the ingot-mould so that liquid uranium will solidify aroundsaid lug. Then, a mere traction on the rod 25 will sulfice to tug alongthe bar being formed in the ingot-mould. The withdrawing process isinitiated by the withdrawal rollers 20, 20 drawing the withdrawal device25.

In the casting plant for tubes with cores (FIG. 5), the graphite core 62goes through the dynamic seal 64 to enter the vacuum chamber.

Said core is then subjected by coil 69 to an induction pre-heating stepwhich causes simultaneous degassing, whereafier it is driven throughingot-mould 9, being kept precisely centered on the axis thereof byrollers 63, 63' and by rollers or skids 68. Uranium will solidify aroundthe graphite bar and thus a cored tube will exit from the ingot-mould.

The cored bar or tube is then driven through cooling jacket 14. The baris drawn towards vacuum chamber (dynamic vacuum lock) 15, throughwithdrawal rollers 20, 20' driven by motor 21, at a given linear speed.Servo-mechanism 22, controlled by temperature-detector 23, acts toadjust the speed of motor 2! to cause the bar to emerge at desiredtemperature from cooling jacket 14, which is of suitably selected lengthto cause adequate radiation cooling of the bars, e.g. down to 800C.Thus, when withdrawn at a speed of 2 cm/s from an ingot-mould having alength of 280 mm, a bar of a 60 mm-diameter will be at a temperature of950C.

The cored bar or tube then enters vacuum lock 15. The threaded seals 33,34, 35 (FIG. 2) are intended for the following pressure differences, intorts from 10' to ID"; from ID to l" from 10" to 1, respectively.Funnel-shaped seals 36, 37 are intended for pressure ratios, in torrs,of l to 10 and 10 to 10'. Finally, pneumatic seal 32 corresponds to thepressure difference, in tons, of from l0 to 10' Besides acting as aseal, pneumatic seal 32 (FIG. 4) has three other functions. Namely, dueto its location,the pneumatic seal serves to prevent ingress of waterfrom spray means. 19. As a matter of fact, nitrogen issuing from thepressure chamber is released downwards, at high speed, along bar B,through an exhaust channel EC, acting as a nozzle-neck, located betweenthe bottom of frustum $2 and the restricted portion of part 50.

Consequently, the nitrogen blast will drive back downwards the finewater droplets sprayed by means 19. Secondly, due to its acceleratedoutwards motion, the nitrogen jet prevents any ingress of oxygen fromthe ambient atmosphere into the pressure chamber.

Finally, the nitrogen jet acts as an adjustable cooling member on thebar issuing from the pneumatic seal. To this end, temperature-detector18 (FIG. I) actuates servo-mechanism 17 which, by regulating thepressure in the nitrogen source 16 and in pressure chamber 15, causesthe gas to exit at a variable velocity and thus adjusts cooling so as tokeep the bar issuing from the pneumatic seal at a fixed temperature,e.g. of about 700C.

The spray means 19 ensures rapid cooling of the bar, serving severalpurposes, viz. apart from thus permitting handling of the cut bars, thespray means prevents the bar from firing as a result of its rapidoxidation in the air and if the alloy is susceptible thereto, it mayeffect a hardening step which, in the present case, is from 700C.

The use of a vacuum chamber 1 having located therein a ladle 2| at1,400C and the temperatureand pressure-adjusting processes allow, on theone hand, obtention of uranium which is very pure since subjected tothorough vacuum degassing at high temperature and, on the other hand,continuous shaping of bars and withdrawal thereof from the vacuumchamber, at high speed, and if required, hardening of the bars underprecise temperature conditions.

It should be noticed that the uranium treatment was described by mereway of example, implying nolimitationtothepresentprocenlnpartieulanthemethod according to theinvention is of high interest for the casting of steels and othermaterials requiring rather intensive dehydrogenation and/ordecarbonization and 8 denitriding steps, said steps being promoted bythe substantial degassing obtained under vacuum.

Moreover,.the insertion of pre-melted metal in the vacuum chamber is nota requisite step. Within the scope of the invention, the metal may bemelted directly within the ingot-mould, either under vacuum by electronbombardment or under a controlled atmosphere (e.g. argon atmosphere attons) by are fu- SlOIl.

Finally, the various temperature and pressure control processes and theuse in the vacuum lock of a number of suction chambers separated bydynamic seals provide great operational safety.

indeed, should some temperature-control device fail, then the othertemperature control devices will sufiice to control the advance of thebar through the vacuum chamber.

At last, in case of abnormal operation of one suction chamber, the pumpsof the other suction chambers have sufficient delivery to maintain saidchambers under the requisite low pressures.

FIG. I shows a modified embodiment according to which there are providedmeans to vibrate the ingotmould in a definite mode and means to controlwith great precision the level reached in the ingot-mould by the liquidmaterials.

in said FIG. 7, there is shown at 101 a circular plate serving as a basefor the device and connected to the vacuum chamber 1. The axis of thiscircular plate coincides with the ingot-mould axis. A cylindricalpassage having a diameter slightly greater than that of the bars to becast is provided through the circular plate, in axial alignment with theingot-mould.

A circular sleeve 102 is secured normally to plate 101 and has a throughbore parallel to the ingot-mould axis- Two further sleeves one of whichis shown at 103, are fixed onto the circular base. The spacings of theaxes of sleeves to the ingot-mould axis all are equal and planes passingthrough the ingot-mould axis and the axes of sleeves are spaced fromeach other at angles of 120 around the axis of the ingot mould. Verticalpedestals, two, 105 and 106, being shown, and a third not being shownare slidable in the bores of the aforesaid sleeves respectively. Acircular plate 108 is secured to the three pedestals 105, etc. somewhatabove sleeves I02, 103, 104. A circular plate 109 is secured onto thetops of the pedestals. A cylindrical copper lining 110 forming the mainbody of the ingotmould is secured to plates 108 and 109. A hollow steelcylinder 111, which is coaxial to the ingot-mould and has a greaterdiameter than the copper lining 110, defines with liner 110 and plates108, 109 a closed space which is filled with water. Said closed space isfed with running water from hoses I12, 113. Said hoses are capable ofwithstanding, when under vacuum, aninternalpressurebysto'ltimeshigherthanatmospherie pressure, without anyleakage towards vacuum.

Two links, one being shown at 114, which are symmetrically arrangedabout the ingot-mould axis are journalled about respective horizontalpins, one being shown at 116, mounted in bearings, one being shown at118, which are attached to plate 108. Said links are operativelyconnected to the ends ofcrank arms, onebeingshownatl20,bypins,oneheingshownat 122.Thecrankarmsaresecuredtoashaftlflwhichis parallel with plate 101 andheld in this position by bearings (not shown) attached to plate 101. Thecrank arms rotate with the shaft 124 when the shaft is operated by acam. A previously known and suitable cam and cam drive arrangement areshown schematically in FIG. 8. The cam is shown at 150 formed with a camtrack 151. A lever 152 pivoted on a bearing 153 fixed with respect tothe plate 101 and parts secured thereto has a follower roller 154engaging the cam track 151. A link 155 is pivoted at 156 to the lever152 and is pivoted at 157 to an arm 158 secured to the shaft 124. Thecam 150 is mounted on a shaft 159 driven in the direction of the arrow aby an electric motor 160. Said cam drives the shaft 124 at a rotationalspeed which is low in the direction corresponding to the descendingmovement of crank arm pivot 157 and high in the opposite direction,corresponding to the ascending movement thereof.

There is shown at 125 the probe of a Geiger counter which extendsvertically besides cylindrical tube 111. Probe 125 is connected to theelectronic circuit of the Geiger counter through a flexible tube 126.

The outlet of the electronic circuit is connected to the servomechanism6 controlling the rate of admission by the plunger 4. A source ofradioactive radiation 127 is so arranged before the ingot-mould that theaxis of the ingot-mould and the axis of probe 125 are within theradiation field. The upper horizontal boundary plane of the radioactiveradiation is at a level slightly above the permissible level of theliquid materials in the ingot-mould.

The jerky ingotmould movement is generated in the following manner Theafore-mentioned cam 150 driven by the electric motor 160 causes theshaft 124 cam driven by an electric motor causes shaft to rotate slowlyby a few degrees in one direction, then to rotate rapidly by the samenumber of degrees in the opposite direction.

When shaft 124 is rotating in the first-mentioned direction, the ends ofthe crank arms 120, which are connected by pins to the link 114 and theother link, not shown, cause the links to move slowly downwards. Whenthe shaft 124 is rotating in said opposite direction, the links arerapidly raised. Said links will impart a reciprocating vertical motionto plate 108 and to all parts mounted thereon, especially pedestals 105and 106 and the third pedestal, not shown. Sleeves 102, 103, the thirdsleeve, not shown, which hold the pedestals in vertical positions allowsliding vertical motion of said pedestals to follow the verticalmovements of the links. Parts 108, 109, 110, 111 are driven by saidlinks in a vertical motion with a slow descending and a rapid ascendingstroke.

During rapid raising of the ingot-mould, the bar being formed isprevented frombeing lifted, especially by means of the withdrawalrollers such as 20, 20'; however, the friction and surface tensionforces might drive along a metal ring of small height, located near themeniscus. When the ingot-mould is driven downwards at a speed slightlyexceeding that of the bar, said ring will be pressed onto the bar andthus again joined therewith.

Provision is made to use the radioactive radiation source 127 such asabove-mentioned and a Geiger counter to control the level reached by theliquid materials in the ingot-mould and to use the level measurementsfrom the thus devised controller for operating the servo-mechanism 6acting to adjust the plunger 4 opening movement and, thereby, the rateof admission of liquid materials.

The radioactive source provided has the advantage of producing radiationwhich is bounded by two vertical planes in close parallel relationship,by a horizontal plane and by a plane which is normal to both verticalplanes and at a definite angle to the horizontal plane; therefore, byprecisely adjusting the position of the radioactive radiation sourcealong two horizontal, mutually perpendicular axes and by suitablycontrolling the direction of said source, both the ingot-mould axis andthe Geiger probe axis canbe brought within the two radiation-boundingvertical planes. By adjusting the height of the radiation source, thehorizontal boundary plane of the radiation can be caused to lie abovethe liquid material level. Such provisions allow the operating staff tohandle safely a rather strong radioactive flux, since the radiation fluxarea is defined by precise geometrical surfaces.

Due to the use of a strong radioactive flux, said flux undergoessubstantial variations to be detected by the probe even when thevariations of the liquid material are small. As a result, theservo-mechanism controlling the admission of liquid materials provideshighly sensitive adjustment.

The major advantage of such a device is to allow simultaneously theobtention of a constant withdrawal rate and very precise adjustment ofthe liquid material level.

Of course, the present invention is not limited to the embodimentsdescribed and shown, but includes within its scope any modification orvariation thereto.

We claim:

1. A plant for continuously casting metal or metal alloy materialcomprising the combination of a vacuum chamber; a ladle located withinsaid vacuum chamber; a flow-rate control system associated with theladle; a distributor provided with a nozzle receiving the liquidmaterial released by the flow-rate control system; an ingot mould havinga liquid material receiving end and an ingot egress end and a watercirculating system; a level detector in said vacuum chamber forcontrolling said first servo-mechanism, said level detector comprising aGeiger tube parallel with the ingot mould axis, and a radioactive sourcehaving its radiation bounded by two vertical planes in close parallelrelationship lying on opposite sides of the ingot mould axis, by ahorizontal plane and by an oblique plane which is normal to saidvertical planes and at an angle of 20-40 to said horizontal plane; avacuum cooling jacket adjacent said ingot mould ingot egress end; adynamic lock comprising a plurality of suction chambers aligned in thedirection of ingot travel therethrough and being connected respectivelyto vacuum passages of successively increasing vacuum ratings; dynamicseals separating said chambers; a pneumatic seal adjacent that suctionchamber which is downstream in the direction of ingot travel throughsaid dynamic lock, said pneumatic seal delivering a neutral gas blastacting simultaneously to seal and as a cooling medium; cooling spraymeans arranged outside the vacuum chamber at the outlet of said dynamiclock, variable speed ingot withdrawal and guiding means; a secondservo-mechanism for varying the speed of said ingot withdrawal andguiding means; a temperature detector at the outlet of the vacuumcooling jacket for controlling the operation of said secondservo-mechanism; vibratory means for imparting to said ingot mould avertical reciprocating movement, said vibratory means comprising a platefixed with respect to said ingot mould, stationary vertical sleeves,pedestals vertically reciprocable in said sleeves and being fixed withrespect to said plate, a motor driven cam, a cam follower, a shaft,means operatively connecting said cam follower to said shaft for rockingthe latter, an arm fixed on said shaft, and link means operativelyconnecting said arm to said plate, said cam being contoured to impart arelatively slow downward movement to said ingot mould and a relativelyrapid upward movement to said ingot mould.

2. A plant for continuously casting metal or metal alloy materialcomprising the combination of a vacuum chamber; a ladle located withinsaid vacuum chamber; a flow-rate control system associated with theladle; a distributor provided with a nozzle receiving the liquidmaterial released by the flow-rate control system; a verseal adjacentthat suction chamber which is downstream in the direction of ingottravel through said dynamic lock, said pneumatic seal delivering aneutral gas blast acting simultaneously to seal and as a cooling medium;cooling spray means arranged outside the vacuum chamber at the outlet ofsaid dynamic lock; variable speed ingot withdrawal and guiding means; asecond servo-mechanism for varying the speed of said ingot withdrawaland guiding means; a temperature detector at the outlet of the vacuumcooling jacket for controlling the operation of said secondservomechanism; the power operated means for reciprocating said ingotmould vertically.

3. A plant according to claim 2 in which said power operated meanscomprises a cam and follower.

4. A plant according to claim 3 in which said cam is contoured to imparta relatively slow downward movement to said ingot mould and a relativelyrapid upward movement to said ingot mould.

5. A plant according to claim 2 in which said level detector isstationary with respect to said ingot mould and is under vacuum.

6. A plant according to claim 2 including, for the production of coredtubes, a second dynamic lock for introducing the core into said vacuumchamber; guiding means for aligning said core with the axis of the ingotmould; and a core heating device for heating said core upstream of saidingot mould.

7. A plant according to claim 6 in which said core heating device isunder vacuum and said second dynamic lock includes, from outside toinside said c amber, a sliding seal surrounding said core; a suctionchamber; and a threaded dynamic seal.

2. A plant for continuously casting metal or metal alloy materialcomprising the combination of a vacuum chamber; a ladle located withinsaid vacuum chamber; a flow-rate control system associated with theladle; a distributor provided with a nozzle receiving the liquidmaterial released by the flow-rate control system; a verticallyextending ingot mould having a liquid material receiving end and aningot egress end and a water circulating system; a first servo-mechanismfor adjusting the flow-rate control system; a level detector forcontrolling said first servo-mechanism; a vacuum cooling jacket adjacentsaid ingot mould ingot egress end; a dynamic lock comprising a pluralityof suction chambers aligned in the direction of ingot traveltherethrough and being connected respectively to vacuum pumps ofsuccessively increasing ratings, and dynamic seals separating saidchambers; a pneumatic seal adjacent that suction chamber which isdownstream in the direction of ingot travel through said dynamic lock,said pneumatic seal delivering a neutral gas blast acting simultaneouslyto seal and as a cooling medium; cooling spray means arranged outsidethe vacuum chamber at the outlet of said dynamic lock; variable speedingot withdrawal and guiding means; a second servo-mechanism for varyingthe speed of said ingot withdrawal and guiding means; a temperaturedetector at the outlet of the vacuum cooling jacket for controlling theoperation of said second servo-mechanism; the power operated means forreciprocating said ingot mould vertically.
 3. A plant according to claim2 in which said power operated means comprises a cam and follower.
 4. Aplant according to claim 3 in which said cam is contoured to impart arelatively slow downward movement to said ingot mould and a relativelyrapid upward movement to said ingot mould.
 5. A plant according to claim2 in which said level detector is stationary with respect to said ingotmould and is under vacuum.
 6. A plant according to claim 2 including,for the production of cored tubes, a second dynamic lock for introducingthe core into said vacuum chamber; guiding means for aligning said corewith the axis of the ingot mould; and a core heating device for heatingsaid core upstream of said ingot mould.
 7. A plant according to claim 6in which said core heating device is under vacuum and said seconddynamic lock includes, from outside to inside said chamber, a slidingseal surrounding said core; a suction chamber; and a threaded dynamicseal.